If something is humorous it's funny. Humorous is a fine tone for toasting at your friend’s wedding, but not so much for the reading of someone's last will and testament.
When we talk about humor, we’re usually talking about something funny. But originally the word humorous had to do with the body’s humors, or moods. If you’re reading a medieval book on medicine, you might find descriptions of humorous maladies. Those aren’t joke sicknesses. But if anyone born after 1700 says something is humorous, it means they think it's funny.